1. Field of the Invention
The present invention relates to a distributed video server system constructed by connecting together a plurality of video recorders, each including an optical disk recorder, through a network.
2. Description of the Related Art
Recently, videocassette recorders, which used to be dominating consumer audiovisual equipment, are gradually being replaced by optical disk recorders, which use a disk storage medium such as a recordable or rewritable DVD (which will be referred to herein as an “optical disk”) to read and write audiovisual data therefrom/thereon by an optical technique. The optical disk has a planar data storage layer on which digital audiovisual data is stored. In performing a read or write operation on such an optical disk, an optical head can access any arbitrary location on the data storage layer in a matter of seconds. Accordingly, even if multiple titles of video data are stored on the same optical disk, any of those titles can be played back in a short time. Also, the optical disk as a storage medium is removable and exchangeable, and there is no storage capacity limit on the optical disk recorder itself. By making use of these advantageous features of the optical disk, various new technologies have been proposed.
For example, Japanese Laid-Open Publication No. 11-260043 proposes the technique of storing reserved program recording information on an optical disk. If the reserved program recording information is stored on a given optical disk, then an optical disk recorder reads that information and makes a timer reservation such that its built-in TV tuner and optical disk drive start writing the designated program at a preset time.
Even if the optical disk, from which the reservation information has been read, is removed from the optical disk recorder after the reservation has been done, that reservation information remains on that optical disk. Accordingly, if that optical disk is loaded into another optical disk recorder, that optical disk recorder can also read the reservation information from the optical disk and can make a reservation of a program to be written on the optical disk in accordance with the reservation information. According to this technique, a program to be recorded is reserved in accordance with the information stored on a given optical disk, and there is no need to make a reservation of the same program all over again if the optical disk is loaded into another optical disk recorder.
Meanwhile, optical disks have also been used as computer data storage media, not just as audiovisual data storage media, and contribute immensely to allowing the user to exchange data with a computer system easily. Thus, Japanese Laid-Open Publication No. 12-90575 proposes that a number of optical disk recorders be used as a so-called “distributed server” by using optical disks as removable high-capacity storage media and by connecting the optical disk recorders with those disks together through a network. Furthermore, Japanese Laid-Open Publication No. 13-268461 discloses a system, which is specially designed to record multiple telecasts on different channels simultaneously by using the tuner of another unit included in the same network.
Furthermore, Japanese Laid-Open Publication No. 12-322826 proposes that digital audio or video data to be moved between servers be encrypted for the purpose of copyright protection of video contents. As used herein, to “move” refers to a particular type of transfer process in which whenever the digital data of a program recorded is transferred from one storage device (e.g., a hard disk drive) to the other storage device (e.g., an optical disk drive), the digital data is automatically erased from the source. Meanwhile, Japanese Laid-Open Publication No. 13-76464 discloses a system in which if such data that was moved from a hard disk drive to an optical disk drive needs to be returned to the original storage device (i.e., the hard disk drive), that data is returned to its original storage location on the hard disk, thereby maintaining original data access information substantially (i.e., just as if that data had not been moved at all).
However, the storage capacities of the two storage media, between which the data should be moved, are not necessarily equal to each other. Nor are the processing capabilities of the two different systems to control the same storage medium, either. For that reason, before data is moved, that data may need to be down-converted. For example, a DVD drive does not support digital audiovisual data of a high definition (HD) resolution. Accordingly, if digital audiovisual data of an HD resolution and of a size of 20 GB, which is now stored on a hard disk, is moved to a single DVD with a storage capacity of 4.7 GB, then the amount of data should be cut down by down conversion. In that case, the data that has been moved to the DVD now should have a standard definition (SD) resolution. As used herein, the “down conversion” means generating data of a smaller size from original data by compressing the original data.
However, the user should know that the DVD drive cannot accept data of such a high resolution. Thus, there is no problem even if the image quality deteriorates to some extent as a result of the move. Nevertheless, if the user wanted to play back the digital audiovisual data, which has now moved to the DVD, at the original HD resolution again, then that should be a problem. This is because the digital audiovisual data, which used to be stored on the hard disk, has already been deleted and the digital audiovisual data currently stored on the DVD now has just a SD resolution as a result of the down conversion.
That is to say, in the prior art, once digital audiovisual data has been down converted as a result of a move, that digital audiovisual data can never be played back at the original resolution.